Investment casting apparatus on framework

ABSTRACT

Apparatus and method for making investment, or lost-wax, castings. A mold cavity and an air passageway are formed in a mold of investment material, and a vacuum is applied to the air passageway to draw molten metal into the details of the cavity. The vacuum is provided by heating water to produce steam in an open chamber and then closing the chamber and condensing the steam.

United States Patent [I91 *Sept. 9, 1975 Hudson INVESTMENT CASTINGAPPARATUS ON FRAIVIEWORK [76] inventor: Billy C. Hudson, 948 CoronadoWay, Livermore Calif. 94550 Notice: The portion of the term of thispatent subsequent to Oct. 17 1989, has been disclaimed.

[22] Filed: Oct. 10, 1972 [21] Appl. No.: 296,291

Related U.S. Application Data [63] Continuation-impart of Ser. No878,111 Nov. 19

1969, Pat. No 3,698,468.

[52] US. Cl 164/255; 164/63 [51) Int. Cl 322d 27/16 [58] Field of Searcht. 164/63, 65, 255, DIG 4 [56] References Cited UNITED STATES PATENTS1,105,425 7/1914 Hart 164/D1G. 4

1,186.558 6/1916 Dunn 11 164/255 X 1,698,197 1/1929 bentz v. 164/D1G. 43353.219 11/1967 Synder 264/87 X 3,698 468 10/1972 Hudson 164/65 XFOREIGN PATENTS OR APPLICATIONS 16314 1910 United Kingdom 164/255 1686849/1921 United Kingdom v. 164/65 Primary ExaminerRobert D. BaldwinAttorney, Agent, or Firm-Flehr, Hohbach, Test, Albritton & Herbert 10Claims, 8 Drawing Figures PATENTED E 1975 SHEET 1 BF 3 4 .7 llllllld VPATENTEU SEP 9 I975 SHEET 2 o 3 PATENTEUSEP mm 3 903 953 sum 3 o 3INVESTMENT CASTING APPARATUS ON FRAMEWORK CROSS REFERENCE TO RELATEDAPPLICATION This is a continuation-in-part of Ser. No. 878,111, filedNov. 19, 1969, now US. Pat. No. 3,698,468, issued Oct. 17, 1972.

BACKGROUND OF THE INVENTION This invention pertains generally to castingprocesses and more particularly to a method and apparatus particularlysuitable for investment, or lost-wax, casting.

The basic principles of investment, or lost-wax, casting were discoveredand applied thousands of years ago in China, Egypt, and other parts ofthe world. The process has been used for hundreds of years for thecasting of statues and other artistic works. More recently it has comeinto use by hobbyists for making small castings, such as jewelry.

The basic steps of the lost-wax casting process include making a waxpattern of the casting to be pro duced, assembling the wax pattern to awax gating and sprue system, investing the wax pattern in an investmentmaterial to produce a mold, removing the wax material from the mold,pouring molten metal into the mold, removing the casting from the mold,and cleaning and polishing the casting.

There is a need for a new and improved method and apparatus which can beutilized by hobbyists in the investment, or lost-wax, casting process.

SUMMARY OF OBJECTS OF THE INVENTION In the method and apparatus of theinvention, a pattern fabricated ofa meltable material is coated withinvestment material and placed in a cradle which is also fabricaated ofa meltable material. The cradle is mounted on a mandrel having a flowpassageway. A flask is placed over the pattern and mandrel and filledwith investment material. The pattern and cradle are then removed fromthe investment material to form a mold cavity and air passageway. Moltenmetal is poured into the cavity, and a vacuum is applied to the airpassageway to enhance the flow of metal into the details of the mold.The vacuum is produced by heating water to produce steam in an openchamber and hereafter closing the chamber and condensing the steam.

It is in general an object of the invention to provide a new andimproved method and apparatus which can be utilized in the investment,or lost-wax, casting process.

Another object of the invention is to provide a method and apparatus ofthe above character which includes heater and tank means for heatingwater and condensing steam to produce a vacuum which is applied to themold cavity to enhance the flow of casting material into the cavity.

Another object of the invention is to provide a method and apparatus ofthe above character which are particularly suitable for use byhobbyists.

Additional objects and features of the invention will be apparent fromthe following description in which the preferred embodiments are setforth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view ofone embodiment of casting apparatus incorporating the present invention,with the investment mold in place.

FIG. 2 is a side elevational view of the embodiment shown in FIG. 1.

FIG. 3 is an enlarged sectional view of a portion of the apparatus shownin FIG. 1, illustrating the interior of the investment mold.

FIG. 4 is an exploded isometric view, illustrating the manner in whichthe investment mold is formed.

FIG. 5 is a front elevational view ofa second embodiment of castingapparatus incorporating the invention.

FIG. 6 is a front elevational view of a third embodiment of castingapparatus incorporating the invention.

FIG. 7 is a front elevational view of a fourth embodiment of castingapparatus incorporating the invention.

FIG. 8 is a front elevational view of a fifth embodiment of apparatusincorporating the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment illustratedin FIGS. 1-4, the casting apparatus comprises an investment mold 10,framework means ll adapted for removably holding the mold, cruciblemeans 12 mounted on the framework means and adapted for holding andpouring molten metal, heating means 13 for melting the metal in thecrucible means, and vacuum means 14 for drawing the molten metal intothe mold.

The framework means 11 includes a horizontally disposed base member 16and a platform member 17. These members are generally rectangular inshape and are conveniently fabricated of a metal such as steel plate. Aplurality of mounting feet 18 are secured to the lower surface of thebase member 16 and adapted for resting upon a suitable supportingsurface such as a table top. The platform member 17 is generallyparallel to and spaced above the base member 16. The platform member issupported by a plurality of spacer members 19 which extend between thebase member and platform member and are attached thereto by conventionalmeans such as welding or bolting.

A threaded elongate member 21 is mounted on the platform member 17 toprovide means for supporting the crucible means 12. The threaded member2| extends vertically through a mounting hole formed in the platformmember 17 and is secured in place by nuts 22 and 23 which engage theupper and lower surfaces of the platform member, respectively. A yokemember 24 is mounted at the upper extremity of the threaded member 21 bymeans of nuts 26. A shaft 27 is pivotally mounted between the arms ofthe yoke 24, and a platform 28 is mounted on the shaft 27. In thepreferred embodiment, the platform is secured to the shaft by means ofrivets. The crucible means 12 is mounted on the platform 28 and isthereby adapted for movement between level and inclined positions. Avertically extending lip 28a is formed at the forward extremity of theplatform 28, and a clamp screw 29 is carried by the platform. The lipand clamp screw cooperate to hold the crucible means on the platform.

The crucible means 12 includes a conventional crucible 31 having a wall32 and a spigot 33. The spigot communicates with the well in such mannerthat when the crucible is in a level position, as illustrated in FIG.

1, molten metal can be retained in the well. When the crucible is in itsinclined position, the molten metal is discharged through the spigot.

It should be noted that in addition to securing the threaded member 21to the platform member 17, the nuts 22 and 23 provide means foradjusting the vertical position of the crucible means 12 above the mold10.

In the preferred embodiment, the heating means 13 includes a source ofcombustible fluid, such as propane gas. As shown in the drawing, thissource is provided by small propane torch of conventional design. Thistorch includes a tank 36 in which the gas is stored, a valve 37 formetering the flow of gas out of the tank, and a tip 38. The tip 38 isdisposed in proximity to the crucible 31, and the tank 36 is mounted onthe framework 11 in such a manner that the position of the tip 38 can beadjusted as desired. The tank 36 is clamped to a pair of parallel,spaced apart rod members 41 by means of resilient spring member 42. Therod members 41 are attached toward their lower extremities to a mountingyoke 43 by conventional means such as welding or riveting. The mountingyoke 43 is pivotally mounted on a shaft 44 carried by another yoke 46which is attached to the rear portion of the platform member 17. Endcaps 47, fabricated of a material having a relatively high coefficientof friction, are provided at the upper and lower extremities of the rodmembers 41. The ends of the resilient spring member 42 are attached tothe mounting yoke 43 and this spring member urges the tank 36 intoengagement with the end caps 47.

Means is provided for adjusting the angle of inclination of the tank 36relative to the platform member 17. This means includes an eyeboltmounting bracket 48 attached to the platform member 17 and turnbucklemeans 49 pivotally connected to the bracket 48 and to the upper portionof one of the rod members 41. The position of the torch can also beadjusted by sliding the tank 36 axially of the rod members 41.

The vacuum means 14 includes a hermetically sealed vacuum chamber 51formed within a spherical container 52. The container 52 is providedwith threaded bushing 53 having a bore 54 communicating with the chamber51. This bushing extends through an opening in the platform member 17,and a nut 56 is threadedly mounted thereon to secure the container 52 tothe platform member. The bore 54 provides means for introducing waterinto the chamber 51, and a conically tapered plug 57 provides means forclosing the bore 54. This plug also serves as a safety valve in theevent the pressure within the chamber becomes excessively high.

Means is provided for heating water Within the chamber 51. This meansincludes a coventional source of hear 58 carried by the base member 16and disposed vertically below the container 52. In the preferredembodiment, the source 58 comprises a container of combustible fuel injellied form. A plurality of locating studs 59 are attached to the basemember 16 to provide means for positioning the fuel supply 58.

A vacuum line 61 is provided for interconnecting the vacuum chamber 51with the mold to provide communication between the chamber and the moldcavity. This line includes a first section 61a communicating with thechamber 51 and connected at one end to a fitting 62 mounted on thecontainer 52. The outer end of the section 61a is connected to the inletside of a valve 63. A seecond section 61b of the vacuum line extendsbetween the discharge side of the valve and a T-fitting 64. The vacuumline 61 also includes an upper section 61c which extends from the upperside of the T-fitting 64 through an opening 66 in the platform 17. Theupper end of the section 610 extends above the platform member and intoa connector 67. The connector 67 is formed to include a passageway 68 toprovide communication between the line 61 and the mold cavity. The outercontour of the connector includes a cylindrical lower section 69, acylindrical upper section 71 of smaller diameter than the lower section,and a conically tapered shoulder 72 intermediate the upper and lowersections. In the preferred embodiment, the connector 67 is fabricated ofmetal and is attached to the line 61 by threads.

The vacuum line 61 is formed to include trap means for preventingforeign matter, such as molten metal and particles of the mold, frombeing drawn into the vacuum chamber 51. This trap means include a trapsection 61d connected to the lower side of the T-fitting 64 and locatedbelow and in axial alignment with the passageway 68 in the connector 67.The cap 73 is removably attached to the lower end of the trap section topermit cleaning of this section.

The valve 63 provides means for controlling the communication betweenthe vacuum chamber 51 and the mold cavity. In the preferred embodiment,this valve comprises a conventional stopcock having a butterfly memberadapted for movement between open and closed positions throughrotational movement on the order of Linkage means is provided forinterconnecting the crucible means 12 and the valve 63 in such mannerthat the position of the crucible corresponds to the position of thebutterfly member in the valve. This means includes a shaft 76 operablyconnected at one end to the butterfly member of the valve and pivotallysupported toward its other end by a bracket 77 attached to the undersurface of the platform member 17. An operating handle 78 is connectednear the outer extremity of the shaft 76 to provide means for rotatingthe shaft. The linkage means also includes a crank 81 attached to theshaft 76 proximate to the handle 78, an elongate member 82 having itsupper end pivotally connected to the rear portion of the crucibleplatform 28, and an adjustable clamp member 83 pivotally connecting thelower portion of the elongate member 82 to the crank 81. The clampmember 83 can be adjusted axially of the elongate member 82 to providemeans for adjusting the length of the linkage and the relative positionsof the crucible and valve. ln FIG. 1, the valve 63 is shown in itsclosed position, and the crucible is level. When the valve is opened byrotating the operating handle 78 in a clockwise direction, the crucibleis moved to its inclined position.

The investment mold 10 is adapted to be removably mounted on the uppersurface of the platform member 17, with the connector 67 extending intothe lower portion of the mold. The mold includes a cylindrical sleeve orflask 86 which preferably has a substantially flat surface 86a at oneend to provide a good sealing surface. A rubber gasket 87 is disposedbetween the surface 860 and the upper surface of the platform member 17to insure a good seal during investment. This sleeve is adapted forholding a conventional investment material 83 which is formed to definea mold cavity 89, a funnelshaped sprue 91, and a gate 92 interconnectingthe sprue and cavity. In addition, the investment material 88 is formedto define air passageways 93 which communicate with the cavity 89through the porous investment material and which are adapted forcommunicating directly with the passageway 68 in the connector 67.Suitable investment materials include refractory material such as silicain the form of quartz or cristobalite, with a gypsum plaster binder.

Operation and use of the apparatus described above and therein themethod of the invention can now be described briefly. Let it be assumedthat the rubber gasket 87 has been placed over the connector 67 and isresting upon the upper surface of the platform member 17. Further let itbe assumed that a pattern 101 fabricated of wax or another suitablematerial has been prepared in the conventional manner and that a waxcolumn 102 has been attached to the pattern to provide means for formingthe gate 92. A cradle 103 for the pattern is formed by bending columnsof wax 104, commonly known as wax wires, or another suitable material,into a form generally corresponding to the contour of the pattern. Thecradle is attached to the upper portion of the connector 67 byadditional wax 106, and this cradle provides means for forming the airpassageway 93. Preferably, the cradle and wax attaching it to theconnector should seal the passageway 68 to prevent investment materialfrom entering this passageway during formation of the mold.

A coating of investment material 107 is formed on the pattern, and thecoated pattern is placed in the eradle, with the wax column for formingthe gate extending in an upward direction. The coating can beconveniently formed by brushing successive layers of investment materialin slurry form into the pattern. It is important that the coating have asufficient thickness to prevent cave-ins between the cavity and the airpas sageways. A thickness on the order of Va inch has been found to givesatisfactory results in casting pieces of jewelry, such as rings.Alternatively, if desired, the coating can be formed on the cradleinstead of or in addition to the pattern.

After the pattern has been placed in the cradle, the sleeve 86 is placedover the pattern, with its lower surface 86a resting on the rubberwasher 87. A slurry of investment material 88 is poured into the sleeveand allowed to harden.

After the investment material has hardened, the mold and rubber gasketare removed from the platform member 17, and the funnel-shaped sprue 69is formed by cutting away a portion of the investment material.

The wax is removed from the hardened mold by conventional means, such asheating in an oven or furnace to a temperature on the order of l,000 to1,200 F. Alternatively, the wax can be removed by means ofasolvent-vapor bath. such as trichloroethylene vapor. After the wax hasbeen removed, the mold is maintained at a temperature on the order of700 to 1,000F, the exact temperature depending upon the metal to becast. Maintaining the mold at this temperature tends to vaporize andeliminate any wax which remains in the mold, and it facilitates the flowof metal in the mold during the casting process.

While the mold is being heated, a vacuum is formed in the vacuum chamber51. For this purpose, the plug 57 is removed and water is introducedinto the chamber through the opening 54. The water is then heated bymeans of heat source 58 until it vaporizes and there is a steady flow ofsteam from the opening 54. The heat source is then extinguished, theplug 57 is replaced and the chamber is allowed to cool. When chambercools to room temperature, the steam will condense, producing a pressureon the order of 1/200 of an atmosphere in the chamber.

After the vacuum has been formed, the metal to be cast is placed in thecrucible 31 and melted by means of the torch 13. When the metal is readyfor casting, the heated mold 10 is replaced on the platform 17, with theconnector 67 by engaging the investment material in a sealingrelationship. The valve 63 is opened by rotating the handle 78 whichcauses the crucible means 12 to move to its inclined position, pouringthe metal into the sprue 91. The molten metal flows downwardly throughthe gate 92 and into the cavity 89. The difference in pressure betweenthe vacuum chamber 51 and the sprue 91 which is exposed to theatmosphere enhances the flow of metal into the details of the cavity.When the casting has cooled, it can be removed from the mold andfinished in a conventional manner.

FIG. 5 illustrates a simplified embodiment of the invention which has aninverted U-shapcd framework 111 fabricated of a suitable material suchas sheet metal. Mandral member 67 is mounted on the upper surface of theframework, and a vacuum tank 112 is mounted below the mandrel member.The tank has a removable stopper 113, and communication between the tankand mandrel member is controlled by a valve 114. Mold 10 is removablymounted on the framework over the mandrel member, as in the previousembodiment. Instead of using a separate crucible, a crucible well 116 isformed in the investment material in the upper portion of the mold.Metal placed in this well is melted by a hand-held torch 117. This torchcan also be used for heating water in tank 112 or, if desired, theapparatus can be placed on a stove to heat the water.

Operation and use of the embodiment shown in FIG. 5 can be describedbriefly. The mold is formed as before, except that a crucible well 116is formed in the upper portion of the investment material. The materialto be cast is placed in this well and melted by torch 117. A vacuum isproduced in tank 112 by boiling water with stopper 113 removed and thencondensing the steam with the stopper in place. When the material incrucible well 116 is molten, valve 114 is opened to draw the materialinto the mold cavity.

The embodiment shown in FIG. 6 is generally similar to that shown inFIG. 5 except that it does not have a mandrel member. Instead, a flatplate 119 is mounted on the upper surface of the framework, and the moldrests on this plate during the casting process. If desired, a gasketsimilar to gasket 87 can be utilized between the mold and plate.

The embodiment shown in FIG. 7 also includes an in verted U-shapedframework within which a vacuum tank 122 having a removable stopper 123is mounted. A mandrel member 67 is mounted on the upper surface of theframework, and a vacuum line 124 extends down from the mandrel member.This line is connected to the vacuum tank through a T-fitting 126 and avalve 127, the latter providing means for controlling communica tionbetween the tank and mold. A trap 128 is also connected to the T-fittingfor preventing foreign matter, such as molten metal and particles of themold from being drawn into the vacuum tank. Mold 10 is mounted overmandrel 67, as before, and it is formed to include a crucible well 116in which material to be cast can be melted. A torch 13] mounted on anadjustable holder 132 provides means for melting the material in thecrucible well. The operation and use of this embodiment are similar tothe operation and use of the embodiment shown in FIG. 5.

FIG. 8 shows an embodiment of the invention which is particularlysuitable for making larger castings. In this embodiment, the frameworkincludes a support stand 136 having a base portion 1360, a pair ofspaced apart upright members l36b and a stop 13642. A crucible 137, moldl0, and vacuum tank 138 are mounted on a pivot arm 139 to form a rigidassembly which is pivotally mounted on the support stand. A valve 141controls communication between the vacuum tank and mandrel 67 in mold10. This valve has a flow control member movable between open and closedpositions in 90 of rotation. The valve member is rigidly affixed to theupright members of the support stand, and the valve serves as a pivotfor the crucible, mold and tank assembly. The valve is closed when theassembly is in the horizontal position. and it is opened by rotating theassembly 90 in the clockwise direction to an upright position. A torch142 is mounted on an adjustable holder 143 for heating material in thecrucible. As illustrated, the torch holder is mounted on the pivot arm,and the torch moves with the rest of the assembly. Alternatively. ifdesired. the torch holder can be mounted on the support stand.

Operation and use of the embodiment shown in FIG. 8 can be describedbriefly. Mold 10 is prepared as before and placed over mandrel member67. With the pivotally mounted assembly in its horizontal position.material to be cast is melted in crucible 137, and a vacuum is formed intank 138. Thereafter. the assembly is swung to its upright position,pouring the material from the crucible into the mold. As the assemblyswings, valve 14! opens, and the vacuum draws the material into the moldcavity.

The invention has a number of important features and advantages. Itprovides a casting method and apparatus which are easy to use andparticularly suitable for use by hobbyists. While only certain presentlypre ferred embodiments have been described herein. as will be apparentto those familiar with the art, certain changes and modifications can bemade without departing from the scope of the invention as defined by thefollowing claims.

I claim:

1. In casting apparatus, a mold comprising a body of investment materialdefining a mold cavity, a framework including a horizontally extendingplatform for supporting the mold in an upright position, tank means forheating water and condensing steam to form a vacuum, means mounting thetank means in a predetermined position beneath the platform and forminga vacuum passageway between the tank means and the mold cavity, amandrel member carried by the framework and extending a substantialdistance into the investment material, said mandrel member having apassageway communicating with the vacuum passageway, 5 one end of themandrel passageway being in close proximity to the mold cavity, andvalve means movable between open and closed positions for controllingcommunication between the tank means and the mold cavity.

2. Casting apparatus as in claim 1 wherein the vacuum passagewayincludes a trap for preventing foreign matter from being drawn into thetank means from the mold.

3. Casting apparatus as in claim 1 wherein the mold is removably mountedon the horizontally extending platform.

4. Casting apparatus as in claim 3 together with a gasket memberdisposed between the mold and the platform.

5. Casting apparatus as in claim 1 wherein the mold is formed to includea crucible well in which material to be cast can be heated and melted.

6. Casting apparatus as in claim 5 wherein the crucible well is formedin the upper portion of the investment material.

7. Casting apparatus as in claim 5 together with means carried by theframework for heating the material in the crucible well.

8. In casting apparatus, an inverted U-shaped framework having agenerally planar base and a pair of depending legs at opposite sides ofthe base for supporting said base in a generally horizontal position, amold comprising a body of investment material defining a mold cavitysurmounted on the base, tank means mounted beneath the base and betweenthe legs of the framework for heating water and condensing steam to forma vacuum, means including a vacuum passageway connected between the tankmeans and the mold cavity, a mandrel mounted on the base of theframework and having a passageway communicating with the vacuumpassageway, said mandrel extending a substantial distance into the moldand into close proximity to the mold cavity, and valve means movablebetween open and closed positions for controlling communication betweenthe tank means and the mold cavity.

9. The casting apparatus of claim 8 wherein the U- shaped framework isfabricated of sheet metal.

10. The casting apparatus of claim 8 wherein the mandrel includes arigid body through which the passageway extends in an axial direction,said body having a cylindrical outer wall portion and a conicallytapered portion adjacent to said cylindrical portion, said conicallytapered portion engaging the investment material in the mold to form avacuum, seal therewith.

* IF i

1. In casting apparatus, a mold comprising a body of investment materialdefining a mold cavity, a framework including a horizontally extendingplatform for supporting the mold in an upright position, tank means forheating water and condensing steam to form a vacuum, means mounting thetank means in a predetermined posiTion beneath the platform and forminga vacuum passageway between the tank means and the mold cavity, amandrel member carried by the framework and extending a substantialdistance into the investment material, said mandrel member having apassageway communicating with the vacuum passageway, one end of themandrel passageway being in close proximity to the mold cavity, andvalve means movable between open and closed positions for controllingcommunication between the tank means and the mold cavity.
 2. Castingapparatus as in claim 1 wherein the vacuum passageway includes a trapfor preventing foreign matter from being drawn into the tank means fromthe mold.
 3. Casting apparatus as in claim 1 wherein the mold isremovably mounted on the horizontally extending platform.
 4. Castingapparatus as in claim 3 together with a gasket member disposed betweenthe mold and the platform.
 5. Casting apparatus as in claim 1 whereinthe mold is formed to include a crucible well in which material to becast can be heated and melted.
 6. Casting apparatus as in claim 5wherein the crucible well is formed in the upper portion of theinvestment material.
 7. Casting apparatus as in claim 5 together withmeans carried by the framework for heating the material in the cruciblewell.
 8. In casting apparatus, an inverted U-shaped framework having agenerally planar base and a pair of depending legs at opposite sides ofthe base for supporting said base in a generally horizontal position, amold comprising a body of investment material defining a mold cavitysurmounted on the base, tank means mounted beneath the base and betweenthe legs of the framework for heating water and condensing steam to forma vacuum, means including a vacuum passageway connected between the tankmeans and the mold cavity, a mandrel mounted on the base of theframework and having a passageway communicating with the vacuumpassageway, said mandrel extending a substantial distance into the moldand into close proximity to the mold cavity, and valve means movablebetween open and closed positions for controlling communication betweenthe tank means and the mold cavity.
 9. The casting apparatus of claim 8wherein the U-shaped framework is fabricated of sheet metal.
 10. Thecasting apparatus of claim 8 wherein the mandrel includes a rigid bodythrough which the passageway extends in an axial direction, said bodyhaving a cylindrical outer wall portion and a conically tapered portionadjacent to said cylindrical portion, said conically tapered portionengaging the investment material in the mold to form a vacuum, sealtherewith.